Gripping mechanism



May 4, 1 4 E. A. MATTESON ETAL GRIPPING MECHANISM Filed NOV. 15, 1941 3 Sheets-Sheet 1 J 2 mm H/ msmw N m E W NT F 4 w WL M m y 4, 1943- E. 'A. MAT'IQ'ESON ET AL I 2,318,242

GRIPPING MECHANISM Filed Nov. 13, 1941' 3 Sheets-Sheet 2 INVENTORS EL W/N A. MATT ESO/V DONALD 57' 06K %n-vw% x4 TTOE/VEKi y 1943- E. A. MATTEsoN ET AL GRIPPING MECHANISM Filed NOV. 13, 1941 3 Sheets-sheaf 3 INVENTORS MATT EJON .DOA/A L Q 1/ 577900? M EL W/ N A FIGS"? Patented May 4, 1943 GRIPPIN G LIECHANISM Elwin A. Matteson and Donald V. Strock, Youngstown, Ohio, assignors to The Aetna Standard Engineering Company, Youngstown, Ohio, a corporation of Ohio Application November 13, 1941, Serial No. 419,008

4 Claims. (Cl. 294-114) This invention relates to gripping mechanism, and more particularly to improved apparatus for gripping the ends of sheet, strip or plate material during the operation of stretcher levelling.

An effective procedure for straightening metal sheets or the like is to subject the sheets to tension, whereby they are stretched sufiiciently to remove irregularities in the sheet. In carrying out such stretcher levelling the sheet is gripped adjacent its ends, and then the gripping means are moved apart to give the desired degree of stretching. With light gauge steel sheet or strip material, and with relatively soft metal sheet or strip such as aluminum, difiiculty has been experienced in providing gripping means which would firmly hold the material during the stretching operation without cutting through and permitting release during stretching. It is among the objects of our present invention to provide an improved gripping mechanism which is particularly adapted for use with aluminum or other soft metal sheets or the like.

Other objects of our invention are: the provision of a gripping mechanism for stretcher levellers which will not cut through the material being gripped, and which is adaptable for gripping sheets having a substantial range of thickness Without any change or adjustment of the gripping mechanism; the provision of a gripping mechanism in which the tension on the sheet being gripped is effective to assist in causing gripping engagement with the sheet; the provision of a gripping mechanism in which the sheet is gripped over a substantial area of its surface as distinguished from a line contact gripping, and in which the gripping member automatically assume parallel relationship on opposite sides of the sheet being gripped regardless of the thickness of the sheet; and the provision of an extremely rugged and simple gripping mechanism which will securely hold thin or soft metal sheets without cutting during a stretcher levelling operation.

The above and other objects of our invention will appear from the following description of a preferred embodiment thereof, reference being had to the accompanying drawings in which:

Figure 1 is a fragmentary plan view of a stretcher leveller illustrating the spaced gripping heads.

' Figure 2 is a side elevation of the apparatus shown in Figure 1. g

Figure 3 is a fragmentary view taken on line 3-3 of Figure 1, and showing the gripper operating mechanism.

, nism taken substantially on lines 5-5 of Figures 1 and 5.

Figure '7 is an enlarged fragmentary vertical cross sectional view taken on line l--'! of Figure 1, and showing the form of the gripper jaws and bars, a sheet being shown in gripped position,

Figure 8 is a, view taken on line 83 of Figure 6 showing one form of the sheet engaging faces of the gripper bars.

The stretcher levelling apparatus, which is par tially shown in Figures 1 and 2, includes a bed or frame portion l, oppositely disposed gripping heads generally indicated at -2 and 3, rods 4 and 5 for securing the gripping head'2 in fixed position on the bed I, and rods 6 and. l which may be connected to any suitable source of power such as a hydraulic cylinder-(not shown) and whereby the head 3 may be moved away from the head 2. The sheet 8, which is illustrated as extending between the gripping heads 2 and 3, will be stretched when the head 3'-ismoved away from the head 2, and an indicating scale 9 may bejpro vided for showing the degree of stretch imparted to the sheet 8. Springs l0 and II are adapted to return the head 3 to its original position when the stretching force is release It will be understood that sheets, strips or plates of any width up to the total width of the gripping heads 2 and 3 may be stretched in this apparatus, and that by adjusting the position of the stationary head 2 relative to the movable head 3, material of diiierent lengths may be accommodated. In the operation of this apparatus a sheet 8 is inserted between the jaws of the gripper heads 2 and 3, the jaws or gripper bars are caused to engage the sheet near its ends, and it is then stretched to the degree necessary to give it the desired stretcher levelling.-

As the gripper heads 2 and 3 are substantially identical except that they are of opposite hand, it will sufiice to describe in detail only the grip ping head 2. The main body or frame member I2 is of generally C-shaped cross section, having spaced edge portions l3 and it between which the mechanism for gripping the sheet is disposed. As will be seen from the drawings, the frame i2 is of heavy, rigid construction, so that it will not yield or spring when the sheet is stretched. In each of the edge portions I3 and I4 of the head I2 a substantially semi-cylindrical bearing groove I5 is formed. These grooves extend across the entire width of the frame I2, and provide a bearing support for the curved bearing portions I9 and I1 of the gripper jaw members, which may be generally referred to as I8 and I9.

The upper gripper jaw member I9is retained in position on the frame I2 by bearing brackets 29, which, as is best seen in Figures 1, 2 and 4, are secured to the end faces of the-frame I2 'by suitable screws 22. In like manner brackets 2i support the lower jaw member I9. These brackets 29 and 2| have bearing portions which rotatably support the extended shaft portions .23 and 24 of the gripper jaw members I8 and I9 respectively. As the jaw members I8 and I9 extend across the fullwidth of the opening in the frame I2, and as the bearing surfaces l6-and I1 thereof (see Fig. '7) are so supported by the brackets 29 and 2| that bearing surfaces I9 and I1 may engage the elongated bearing surfaces I5 in the frame I2, a large bearing area is provided for supporting the load imposed upon the gripper jaws I8 and I9 during stretching of a sheet.

At the inner faces 25 and 23 of the gripper jaws I8 and I9, substantially semi-cylindrical bearing surfaces 21 and 28 are formed which extend across the width of the gripper jaws I9 and I9, which, it will be understood, extendacross substantially the full widthof the frame I2- Disposed in these bearing grooves .231 and 28are the gripperbars 29 and 39 which, as is clearly seen in Figure '7, are round in cross section except where they are flattened to form their sheetgripping faces. A bracket 3I (Fig. 4) is attached to the end of the inwardly projecting portion of the gripper jaw I8 by means of screws 32. This bracket carries an inwardly extending pin or shaft 33 which projects into a suitable bore 34 (Fig. 6) in the top gripper bar 29. The center of the shaft 33 lies substantially on the center of the bearing groove 21. A similar supporting means for the upper gripper bar 29 is provided at the opposite end of frame I2, and thus it will be seen that the gripper bar 29 is supported at its opposite ends for rotation in the groove 21. This rotation, however, is limited by a pin 35 which projects from the end of gripper bar 29 through a hole 39 in the end plate or bracket 3i. I

Thus the gripper bar 29 can only rotate on the shaft 33 until the pin 35 strikes a side of the hole 36. By arranging the hole 36 and stop pin 35 as illustrated, the gripper bar 29 is maintained with its inner, generally planar, gripping face 31 facing downwardly in a more or less horizontal position. By providing the stop pin 35 the gripping face 31 is always retained in position to receive the sheet and the gripper bar 29 cannot rotate on its pivotal support to permit the gripping face 31 to be located above instead of below the supporting shaft 33.

The lower gripper bar 39 is similarly supported on pins or shafts 38 mounted on brackets 39, and is provided with a suitable pin 49 disposed in a hole 4I in bracket 39. vAs is indicated in Figure 6, sufiicient clearance is provided between the shafts 33 and 38 and the bores therefor in gripper bars 29 and 39 to permit the outer cylindrical bearing surfaces of the gripper will be angularly disposed relative to each other as is shown in Figure 4. The greater the pull on the strip 8 the greater will be the tendency for the jaws I8 and I9 to swing about their pivotal supports 23 and 24 into alignment and the greater will be the gripping pressure applied by the-gripper bars against the opposite sides of the sheet 8. Thus the stronger the pull on the sheet the more securely it is griped between the jaws of the gripping mechanism and, due to the pivotal support of the gripper bars 29 and 39 'on-the shafts 33 and 38, sheets of different thickness may be accommodated without change or adjustment of the apparatus as the bars Hand 39 will automatically rotate on their pivotal supports into gripping position with their gripping faces parallel.

The capacity .of our improved gripping jaws is limited only by the degree of rotary movement permitted to the gripper bars 29 and 39 by their stop pins 35 and 49. In Figure 5 the gripping faces of the bars 29 and 39 are considerably far- I ther apart than they are in Figure 4. Thus Figure 5 may be considered to illustrate either the position which the parts would assume when a sheet or strip of the thickness of sheet 8 was being inserted, or the position they would assume when a sheet of maximum thickness was being gripped. The thickness of the material being handled can be reduced down to a minimum and still effective gripping action will be obtained because the generally planar faces 31 and 42 of the gripper bars 29 and 39 will engage each other before the center lines of the gripper jaws I8 and I9 become aligned in vertical straight line.

As seen in Figure 8 the gripping faces 31 and 42 are preferably provided with knobs or projections which assist in securing a firm grip on the sheet being stretched. These knobs or projections may take various forms, but as illustrated they comprise staggered lugs 43 extending upwardly from the lower gripping face 42, and similarly staggered lugs 44 projecting downwardly from the upper gripping face 31. As is illustrated in Figure 8, the upper lugs 44 are preferably arranged above the spaces between the lower lugs 43, so that when the gripping faces move together during operation of the apparatus the opposed lugs will be offset or out of alignment and will tend to indent or deform the sheet and substantially hold it against slipping during the stretching operation. This lug arrangement provides a firm grip across the entire width of the sheet, even though the sheet thickness may vary somewhat, because the offset top and bottom lugs slightly deflect or indent the material and such indentation will occur even though the sheet may vary slightly in thickness across its width.

By providing the floating, pivotally supported gripper bars 29 and 39 having gripping faces which may be described as generally planar" as distinguished from the curved or sharp edge gripping elements of prior devices of this general type, we are able to so distribute the gripping load that cutting through of soft or very thin sheets is effectively prevented while at the same time positive non-slipping gripping is obtained. It will be understood that in some instances it might be desirable to make the gripping faces 31 and 42 smooth and free from lugs or projections or to change the form of the surface roughening, and

we intend to include in the term generally planar, which we have used in this specification and in the appended claims to describe these faces, either smooth or roughened gripping faces.

In the operation of our apparatus it is necessary to open the gripping jaws to permit a sheet to be inserted therein, and to close them with suflicient force to give a gripping action which will hold the sheet firmly with a minimum of swinging movement of the gripping jaws l8 and I9 about their pivotal supports 23 and 24 during the stretching operation. We accomplish this by securing arms 45 and 46 to the projecting shaft portions 23 and 24 of the gripping jaws l8 and I9. Arm 45 carries a gear segment portion 41 and arm 45 carries a similar gear portion 48. As the upper arm 45 is located outside of the lower arm 46, as is clearly seen in Figure 1, these arms may have relative rotary movement without interference with each other. Gear segment 41 on arm 45 engages a gear 49 rotatably mounted on a sub shaft 55 carried by the frame l2, and the gear segment 48 on the lower arm 46 engages a similar gear which is carried by a stub shaft 52 which is also supported by the frame l2. Gears 49 and 5| mesh, as is seen in Figures 2 and 3, and an operating lever or handle 53 is secured to the gear 5| so that movement of the lever 53 will cause rotation of gear 5|.

Thus when the lever 53 is moved upwardly, as viewed in Figure 2, the arm 46 will be moved downwardly and the lower gripper jaw IE will be moved in counterclockwise or opening direction, as seen in Figures 2, 4 and 5. At the same time the arm 45 will be moved upwardly, which will move the shaft 23, to which it is keyed, in clockwise direction as seen in Figures 1, 4 and 5, causing the jaw l8 to move clockwise in opening direction. In like manner, when the lever 53 is moved downwardly the gripping jaws l8 and I9 will be moved toward the right as seen in Figure 4, causing the gripping faces 31 and 62 to approach each other and grip the material which may be disposed therebetween.

After a sheet has been gripped in the heads 2 and 3 b moving the handles 53 and 53' as described above, and after the sheet has been subjected to the desired stretching, the handles 53 and 53 are moved upwardly to open the jaws and release the stretched and levelled sheet. W'hile open another sheet is inserted in position, and the gripping and stretching operation repeated.

The heavy frame I2 of our gripping head is made sufiiciently strong to resist bending or distortion of the gripping jaws I3 and I9 during stretching, and thus a firm grip is assured across the entire width of the sheet being handled. Our floating gripping bars having substantially planar gripping faces of relatively large area make possible eflicient gripping of materials of a wide range of thickness and, as explained above, are particularly suited for, but not limited to, the gripping of soft metal sheets such as aluminum or Duralumin of the type extensively used in modern aircraft production.

Although we have described in considerable detail the illustrated embodiment of our invention, it will be understood by those skilled in the art that various modifications may be made in 3 the particular form and arrangement of the elements making up our gripping mechanism. We do not therefore wish to be limited to the exact apparatus herein shown and described, but claim as our invention all embodiments thereof coming within the scope of the appended claims.

We claim:

1. In gripping mechanism of the type described, a frame member having an elongated opening extending along one side thereof, a groove of arcuate transverse cross section disposed at one edge of said opening, a second groove of arcuate cross section disposed on the other edge of said opening opposite to said first named groove, jaw members supported in each of said grooves, said jaw members each having an arcuate bearing portion adapted to engage the arcuate groove in which the jaw member is supported and shaft portions projecting from each end of said bearing portions, and said jaw members each also having an elongated arcuate gripper bar supporting groove, gripper bars in said jaw grooves, said gripper bars having arcuate groove engaging surfaces and generallyv planar work engaging areas, means independent of said jaw grooves for rotatably supporting said gripper bars in said jaw grooves, means for limiting the rotational movement of said gripper bars, means on said frame member for pivotally supporting said shaft portions of said jaws, and means for swinging said jaws on said supporting means toward and away from each other whereby sheet material may be gripped between the work engaging portions of said rotatable gripper bars and released therefrom.

2. In gripping mechanism of the type described, a frame, a pair of jaw members pivotally supported on said frame for movement into and out of gripping position, and gripper bars supported by said jaws for limited rotation relative thereto, said gripper bars having opposed work-engaging faces, said faces each having projecting portions and recessed portions, the projecting portions on one of said faces being disposed opposite the recessed portions on the other of said faces.

3. In gripping mechanism of the type described, a frame member having an elongated opening extending along one side thereof, a groove of arcuate transverse cross section disposed at one edge of said opening, a second groove of arcuate cross section disposed on the other edge of said opening opposite to said first named groove, jaw members supported in each of said grooves, said jaw members each having an arcuate bearing portion adapted to engage the arcuate groove in which the jaw member is supported and shaft portions projecting from each end of said bearing portions, and said jaw members each also having an elongated arcuate gripper bar supporting groove, gripper bars rotatably mounted in said jaw member grooves and having work engaging portions, means on said frame member for pivotally supporting said shaft portions of said jaw members, and means for swinging said jaw members on said supporting means toward and away from each other whereby sheet material may be gripped between the work engaging portions of said rotatable gripper bars and released therefrom.

4. In gripping mechanism of the type described, a frame member having an elongated opening extending along one side thereof, a groove of arcuate transverse cross section disposed at one edge of said opening, a second groove of arcuate cross section disposed on the h r e g said. p n g ppos te to said fir t na ed. ro e, j w mem er ppor ed in each of said grooves, said jaw members each having an arcuate bearing portion adapted to engage the arcuate groove in which the jaw member is supported and shaft portions projecting from each of said bearing portions, gripper bars rotatably supported by said jaw members and having generally planar work engaging portions, means on said frame member for pivotaily supporting said shaft portions of said jaw members, and means for swinging said jaw members on said supporting means toward and away fromeach other whereby sheet material may be gripped between the work engaging portions of said rotatable gripper bars and released therefrom.

ELWIN A. MA'I'I'ESON. DONALD V. STROCK. 

